Method for controlling retransmission of information using state variables in radio communication system

ABSTRACT

A method for re-transmitting data or control information in a radio link control layer relates to determining whether re-transmission will be ended by comparing a number of transmission with a critical value when the transmission of data or control information has successively failed. The retransmission cycle is comprised of the steps in the order of transmitting information, checking the transmission failure with exit, and counting the transmission number with exit. Therefore, the present invention makes any transmission be checked and prevents wasting radio resource which can occur in re-transmitting data or control information in UMTS mobile communication system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/190,912, filed Jul. 8, 2002, now U.S. Pat. No. 7,242,670, whichpursuant to 35 U.S.C. §119 (a), claims the benefit of Korean PatentApplication Nos. 2001-40711, filed on Jul. 7, 2001, and 2001-51865,filed on Aug. 27, 2001, which are hereby incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for re-transmitting data orcontrol information in the radio link control layer of an IMT-2000 radiocommunication system and particularly, to a method for re-transmittingdata or control information in the radio link control layer, capable ofpreventing waste of radio resource and errors by checking failure of thelast transmission and performing the next process, when the number ofthe transmission of data or control information reaches a critical valueby continuous transmission failure of data or control informationbetween the radio link control layers of sender and receiver.

2. Description of the Related Art

A Third Generation Partnership Project (hereinafter, referred to as3GPP) was formed by national or international or regionalstandardization organizations, such as ETSI of Europe, ARIB/TTC ofJapan, T1 of USA, CWTS of China, and TTA of Korea in order to make adetailed specification of a European type third generation mobilecommunication system (IMT-2000 system). This system is called as UMTS(Universal Mobile Telecommunications System). UMTS adopted WCDMA(Wideband Code Divisional Multiple Access) technology as a radio accessnetwork technology. UMTS is being developed based on the General PacketRadio Service (GPRS) making its root on a packet-switched network andfurther based on the Global System for Mobile Communications (GSM)making its root on a circuit-switched network. In addition, the thirdgeneration mobile communication systems which are able to providemultimedia services, such as voice, video, and data, are underdevelopment in the above partnership.

The International Telecommunication Union (ITU) which is a subsidiaryorganization of the United Nations (UN) has the authority to establishthe standards of international telecommunication. The 3GPP intends theinternational standards and suggests its own IMT-2000 standards to theITU, which is different from the other organization 3GPP2.Conventionally, the radio access technology of the standards is calledas W-CDMA and IMT-2000 technology standard, and also includes UniversalMobile Telecommunications System (UMTS).

The 3GPP includes five technical specification groups (hereinafter,referred to as TSG) in order to operate the project and to develop thetechnology rapidly and effectively. And the respective TSG takes acharge of development, approval, and management of a referencespecification of related area. Among those groups, a radio accessnetwork (hereinafter, referred to as RAN) group develops a function,requirements of a user equipment and UMTS terrestrial radio accessnetwork (hereinafter, referred to as UTRAN), and the specification foran interface under an object of defining a new radio access network inthe third generation mobile communication system.

The TSG-RAN group includes a plenary group and four Working Groups. Thefirst Working Group (WG1) develops specification of the physical layer(first layer), the second working group (WG2) defines functions of thedata link layer (second layer) and network layer (third layer). Also,the third working group determines specifications of an interface amonga base station in the UTRAN, Radio Network Controller (hereinafter,referred as RNC) and a core network and the fourth working group discussrequired conditions about the radio link capacity and requirements forthe radio resource management.

FIG. 1 shows a structure of a radio interface protocol according to the3GPP radio access network.

The radio interface protocol between a user equipment and UTRAN iscomposed of a physical layer, data link layer and network layer inparallel. Vertically, it includes a control plane for transmitting acontrol signal and a user plane for transmitting data information.

Describing FIG. 1 in more detail, the control plane includes a RadioResource Control Layer (hereinafter, referred to as RRC), Radio LinkControl Layer (hereinafter, referred as RLC), Medium Access ControlLayer (hereinafter, referred as MAC) and Physical Layer. The user planeincludes a Packet Data Convergence Protocol (hereinafter, referred asPDCP), RLC layer, MAC layer and physical layer.

The physical layer provides information transmission service to theupper layer using various radio transmission technologies. It isconnected with the MAC layer which located at the upper portion by atransport channel and through the channel, data are moved between theMAC layer and physical layer. The transport channel is divided into adedicated transport channel and a common transport channel according towhether it is monopolistically used by a user equipment or can be sharedand used by a number of user equipments.

The MAC layer provides a re-allotting service of MAC parameter forallotting and re-allotting radio resource. The MAC layer is connectedwith the RLC layer by the logical channel and various logical channelsare provided according to the kind of transmitted information.Generally, in case of transmitting information of the control plane, acontrol channel is used and in case of transmitting information of theuser plane, a traffic channel is used.

The RLC layer provides radio link setting and canceling service andperforms segmentation and concatenation of a RLC Service Data Unit(hereinafter, referred as SDU) which came from the upper layer of theuser plane.

The header information is added to the RLC SDU and transmitted to theMAC layer in the form of the Protocol Data Unit (hereinafter, referredas PDU).

The PDCP layer is located at the upper portion of the RLC layer totransmit data by converting the data transmitted through internetnetwork protocol, such as IPv4 or IPv6 into data in the form which fitsthe RLC layer. Also, data can be efficiently transmitted through radiointerface by reducing unnecessary control information which is used in awire network. This function is called as Header Compression and forinstance, it can be used for reducing the amount of header informationfor TCP/IP.

The RRC provides an information broadcast service for broadcastinginformation to every user equipment located in a predetermined area.Also, the RRC takes the charge of control plane signal processing forexchanging control signal in the third layer and has functions ofsetting of radio resource between the user equipment and UTRAN,maintaining and canceling of the same. Particularly, the RRC hasfunctions of setting, maintaining and canceling of a radio bearer andallotting, repositioning or canceling of radio resource used for radioresource access. At this time, the wireless bearer means a service whichis provided by the second layer in order to transmit data between theuser equipment and UTRAN. Namely, setting a radio bearer means thatcharacteristics of protocol layer and channel which are necessary forproviding a predetermined service are defined and each concreteparameter and operation method are set.

Hereinafter, the RLC layer will be described in more detail.

The RLC layer performs segmentation and concatenation of the RLC SDUwhich comes from the upper layer and composes the RLC PDU by adding theRLC header to the RLC payload which is composed after the operations ofsegmentation and concatenation. Since the RLC PDU header can includeserial number, the receiver can detect the RLC PDU which is damaged whenit is transmitted by checking the serial number of the received RLC PDUand can ask the sender for re-transmitting of the corresponding PDU.

The process that the RLC SDU are converted into an RLC PDU by thefunctions of segmentation and concatenation is shown in FIG. 2. As shownin FIG. 2, an RLC PDU can include one or more RLC SDU and an RLC SDU canbe divided into a number of RLC PDU.

The operation of RLC layer includes three types of modes according tothe functions and they are transparent mode, unacknowledged mode andacknowledged mode.

First, in case of operating the transparent mode, no header informationis added to the RLC SDU which came from the upper layer. Generally, inthe transparent mode, the RLC SDU segmentation and concatenation are notused, but exceptionally, the operations of segmentation andconcatenation can be applied to the transparent mode according to thesetting of the radio bearer

Second, in case operating the unacknowledged mode, re-transmission isnot supported even if the transmission is failed. Therefore, even if thedata are damaged or there occurs problems in transmitting the data andthe related data are discarded. AS services which can use theunacknowledged mode, there are a cell broadcast service, voice over IPwhich uses the IP network and the like.

Finally, if the RLC layer operates in the acknowledged mode,re-transmission is supported in case of packet transmission failure.Namely, the sender RLC layer receives the state information with whichsuccess of transmission can be judged from the receiver and retransmitsthe RLC PDU which requires re-transmission.

The state information including the information of the lost PDU isloaded in the Status PDU and transmitted by the receiver. The Status PDUcan be transmitted from the sender to the receiver, and at this time,the sender sends the MRW (Move Receiving Window) instruction.

When the RLC layer operates in the acknowledged mode, the RLC PDUs arestored in the RLC buffer in the order according to the serialinformation in the header. The stored RLC PDUs are delivered to the MAClayer as many as the MAC layer requires, and generally, transmission isperformed according to the order of the serial number. Since the RLC PDUsent from the sender first time are transmitted in the order of theserial number, the receiver RLC layer can determine the lost RLC PDU byobserving the serial numbers received.

For example, if the serial numbers of the received RLC PDU are #23, #24,#25, #32 and #34, the RLC PDUs having the serial numbers of #26 to #31and #33 are presumed to be lost. The receiver checks the serial numbersof the received RLC PDU and transmits the status PDU including theinformation of positive acknowledgement or negative acknowledgement tothe sender, thus to support the process of re-transmission of thesender.

Generally, the RLC layers of the sender and receiver, respectively, havea transmission window and receiving window. The transmission windowmeans the extent of the RLC PDU that the sender can send at once, andthe receiver can receive only the PDUs having serial numbers which arein the receiving window and the PDUs having serial number which deviatefrom the receiving window. Similarly, the receiver can receive only thePDUs having the serial numbers which are in the receiving window, andthe PDUs having the serial numbers which deviate from the receivingwindow are discarded as soon as they are received.

The sender manages the state variables which are related to there-transmission function of data. The state variables are, VT (DAT), VT(MRW) and VT (RST).

In the above, the VT is an abbreviation of “Variable for Transmission”,the DAT is “Data”, the MRW is “Move Receiving Window”, and RST is“Reset”.

Hereinafter, the state variable will be described with reference toaccompanied drawings.

FIG. 3 is a flow chart showing the process for re-transmitting the dataor control information of the RLC using the conventional state variable.

First, the state variable is set to 0. Then the state variable relatedto the corresponding information is increased by 1 after suchinformation concerning the radio link control layer has beentransmitted. If the value of the state variable is smaller than thecritical value, by comparing the size of the state variable and thecritical value which was already set, the information is transmittedagain. At each time the information is transmitted, the state variableis increased by one. Finally, when the state variable becomes same as orlarger than the critical value, the re-transmission process isterminated and the sending and receiving setting is converted to performa new process (steps 31, 32, 33, 34 and 35).

FIG. 4 is a flow chart showing the RLC PDU re-transmission processparticularly using the state variable VT (DAT).

The VT (DAT) indicates the number of transmission of a specific RLC PDUin the sender RLC layer. Whenever the RLC PDU is sent, the VT isincremented by 1. At this time, a state variable VT (DAT) exists forrespective RLC PDU. If the above value becomes same as or larger thanMaxDAT corresponding to the critical value to prevent the specific RLCPDU from being constantly re-transmitted, all the SDU related to thecorresponding PDU are discarded and instruction of Move Receiving Window(hereinafter, referred as MRW) is performed. At this time, the MRWinstruction is transmitted in the form of a super field which comprisesthe status PDU sent from the sender and the super field is called as aMove Receiving Window Super Field (steps 41, 42, 43, 44, 45 and 46).

FIG. 5 is a flow chart showing a process of re-transmitting the MRWinstruction particularly using the state variable VT (MRW) in theprocesses for re-transmitting information in FIG. 3.

The MRW instruction is sent when there is needed to move the receivingwindow in case the VT (DAT) value is same as or larger than MaxDAT orfor another reasons. At this time, The receiving window instruction mustbe set considering all of data which are affected by discard of thecorresponding PDU. For example, in case a RLC SDU is composed of anumber of RLC PDU and the VT (DAT) of the first PDU becomes same as theMaxDAT, if the first PDU is discarded, the corresponding SDU no longerhave any value as data and accordingly, all of the RLC PDU including thecorresponding SDU must be discarded. At this time, the MRW instructionmust include information of all of the PDU which were discarded.

The VT (MRW) means the number that the MRW instruction is sent and thevalue is increased by one whenever the MRW instruction is sent. Thesender drives Timer_MRW which is a corresponding timer after the MRWinstruction is sent. If MRW_ACK which is a positive response informationof the MRW instruction cannot be received until the timer is expired,the MRW instruction loading the same information is re-transmitted.

When the value of VT (MRW) becomes same as or larger than the MaxMRWwhich corresponds to the critical value, the RLC layer determines thatthe MRW instruction can no longer be performed and resets the operationof the RLC layer (steps 51, 52, 53. 54 and 55).

FIG. 6 is a flow chart showing the process of re-transmitting the RST ofthe RLC layer using the state variable VT (RST) in the processes forre-transmitting information in FIG. 3.

The reset instruction is performed by sending the RESET PDU to thereceiver in case the VT (MRW) value is the same as or larger than theMaxMRW, or the operation of the RLC layer is reset by another reasons.The sender drives Timer_RST which is a related timer when the RESET PDUis transmitted. If the RESET ACK PDU, which is positive responseinformation, is not received from the receiver until the timer isexpired, an identical RESET PDU is re-transmitted.

The VT (RST) represents the number that the RST instruction is sent andthe value is increased by one whenever the sender sends the RESET PDU.When the VT (RST) becomes the same as or larger than the MaxRST, the RLClayer determines that further restoration is impossible, notifies suchcondition to the upper layer and stops the operation (steps 61, 62, 63.64 and 65).

The RLC layer obtains various information which is necessary forre-transmission of the RLC PDU and operation of the RLC layer withoutany help from the upper layers, thus to make a root to be independentlyoperated.

In addition, the above described state variable VT (DAT), VT (MRW) andVT (RST) is increased by one whenever the corresponding information(respectively, RLC PDU, MRW instruction and RESET PDU) is transmitted asin FIGS. 3 to 6. When the value reaches the critical or threshold value(respectively, MaxDAT, MaxMRW, Max and RST), the corresponding processis terminated and additional operations are requested. At this time,problems of the re-transmission method according to the respective statevariables will be described as follows.

First, the problems in the re-transmission method of the RLC PDU will bedescribed. If the present value of VT (DAT) is MaxDAT-1 and negativeresponse is received from the receiver, the sender re-transmits thecorresponding PDU and increases the value of the VT (DAT) by 1.

At this time, since the value of the VT(DAT) became the same as theMaxDAT, the sender immediately discards the corresponding RLC PDU andRLC SDU and sends the MRW instruction. Since the MRW instructionincludes information on discarding of the RLC PDU which was sent rightbefore, the receiver must discard it even if the receiver received thecorresponding RLC PDU successfully. Therefore, the PDU which was sentright before and information on discarding of the RLC PDU can betransmitted almost simultaneously and accordingly, in conclusion, theRLC PDU is unnecessarily transmitted and resource is wasted.

Second, the problems on the method for re-transmitting the MRWinstruction will be described as follows. If the present value of the VT(MRW) is MaxMRW-1 and if the MRW_ACK is not received before the drivenTimer_MRW is expired, the sender re-transmits an identical MRWinstruction and the value of the VT (MRW) is increased by 1.

At this time, since the value of the VT (MRW) becomes the same as theMaxMRW, the process of moving the receiving window is immediately endedand the RESET PDU is sent to the receiver. Since the transmitted resetinstruction nullifies the MRW instruction which was sent right beforeand synchronizes the RLC layer of the receiver, the MRW instruction cannot display the effects even if it was successfully received at thereceiver, and the RLC layer of the receiver performs the resetinstruction. Therefore, in conclusion, the MRW instruction isunnecessarily transmitted and resource is wasted.

Third, the problems on the re-transmission method of the RLC resetinstruction will be described as follows. If the present value of the VT(RST) is MaxRST-1 and the RESET ACK PDU is not received before thedriven Timer_RST is expired, the sender re-transmits the RESET PDU andincreases the value of the VT (RST) by 1.

At this time, the RLC layer immediately stops every operation since thevalue of the VT (RST) became the same as the MaxRST, and notifies to theupper layer that the reset process of the RLC layer has failed. In thiscase, since the RESET PDU, which was sent right before, cannot displaythe effects even if the receiver received it successfully, thecorresponding RESET PDU is unnecessarily transmitted and resource iswasted.

As in the above cases, in the conventional method for re-transmittingdata or control information, the data or control information may beunnecessarily transmitted. Also, if such re-transmission method is used,serious errors in operating the system can occur. For instance, when thevalues of the MaxDAT, MaxMRW and MaxRST (which are critical or thresholdvalues of the respective state variables) are set as “1”, the value ofthe VT (DAT) becomes “1” after initially transmitting a specific PDU andsender sends the MRW instruction on the PDU which was transmittedimmediately. After initially sending the MRW instruction, the value ofthe VT (MRW) becomes “1”, and accordingly, the RESET PDU is immediatelytransmitted. Also, the value of the VT (RST) becomes “1” right after theRESET PDU is transmitted and the sender notifies the upper layer that anerror is occurred. Namely, in case the critical value of the statevariable is set as “1”, the system cannot be operated normally.

SUMMARY OF THE INVENTION

Therefore, to solve the above problems related to the method forre-transmitting the above data and control information, an object of thepresent invention is to provide a method for retransmitting information,such as packet data or control information, that obviates theabove-described problems.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, are-transmission method for the data or control information of the RLCcomprises, setting the state variable of an information unit as 0;transmitting said information unit to the receiver; confirming successof the transmission; increasing the state variable related to thecorresponding information unit by 1; comparing the state variable withthe critical value; changing the state of sending and receiving, if thestate variable is not smaller than the critical value or repeatingtransmission of the information unit, if the state variable is smallerthan the critical value.

For Example:

1. re-transmission of RLC PDU: when the value of the state variable VT(DAT) is same as or larger than MaxDAT, which is the critical value, thesender performs Move Receiving Window instruction without retransmissionof RLC PDU.

2. re-transmission of MRW instruction: when the value of the statevariable VT (MRW) is the same as or larger than MaxMRW, which is thecritical value, the sender performs RLC reset instruction withoutretransmission of MRW instruction.

3. re-transmission of RLC Reset PDU: when the value of the statevariable VT (RST) is same as or larger than MaxRST, which is thecritical value, the sender reports the status to upper layer withoutretransmission of RLC Reset PDU. According to one embodiment of thepresent invention, a method for re-transmitting packet information in aradio link control layer of a radio communication system comprisesassigning a predetermined value to a reference value; comparing a statevariable with the reference value; transmitting a packet informationfrom a transmitting device to a receiving device if the state variableis less than the reference value or changing the state of sending andreceiving without transmitting a packet information from a transmittingdevice to a receiving device, if the state variable is not smaller thanthe reference value; incrementing the state variable by an incrementalvalue if said packet information is transmitted again.

According to another aspect of the present invention, the radiocommunication system comprises communication between a mobile userequipment and a network apparatus. Also, the packet information used insuch system preferably comprises at least one of user data or controldata used in the radio link control layer. The packet information maycomprise a Move Receiving Window (MRW) instruction or a resetinstruction of the radio link control layer.

According to another aspect of the present invention, the state variableis associated with transmission of at least one of data, move receivingwindow instruction and reset instruction. Similarly, the reference valueis associated with transmission of at least one of data, move receivingwindow instruction and reset instruction.

According to another embodiment of the present invention, a terminalequipment used in a radio communication system for re-transmittingpacket information to a network system comprises a plurality of controllayers, each layer capable of communicating with a corresponding layerof the network system; a radio link control layer of the plurality ofcontrol layers of the terminal equipment assigning a predetermined valueto a reference value, comparing a state variable with the referencevalue; and the radio link control layer transmitting a packetinformation from a transmitting device to a receiving device if thestate variable is less than the reference value, or changing the stateof sending and receiving without transmitting a packet information froma transmitting device to a receiving device, if the state variable isnot smaller than the reference value, incrementing the state variable byan incremental value if said packet information is transmitted again.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the Drawings:

FIG. 1 shows a structure of a radio interface protocol according to the3GPP radio access network;

FIG. 2 is a view showing a process that the RLC SDU are converted into aRLC PDU by the functions of segmentation and concatenation;

FIG. 3 is a flow chart showing the conventional process forre-transmitting the data or control information of the RLC using thestate variable;

FIG. 4 is a flow chart showing the conventional re-transmission processof RLC PDU particularly using the state variable VT (DAT);

FIG. 5 is a flow chart showing the conventional process ofre-transmitting the MRW instruction particularly using the statevariable VT (MRW);

FIG. 6 is a flow chart showing the conventional process ofre-transmitting the RST of the RLC layer using the conventional statevariable VT (RST);

FIG. 7 is a flow chart illustrating a process for re-transmitting dataor information among RLC layers, using the state variable in accordancewith a preferred embodiment of the present invention;

FIG. 8 is a flow chart illustrating the process of re-transmission ofRLC PDU using the state variable VT (DAT) in accordance with thepreferred embodiment of the present invention;

FIG. 9 is a flow chart illustrating the process of re-transmission ofthe MRW instruction using the state variable VT (MRW) in accordance withthe preferred embodiment of the present invention;

FIG. 10 is a flow chart illustrating the process of re-transmission ofthe reset instruction of the RLC layer using the state variable VT (RST)in accordance with the preferred embodiment of the present invention;

FIG. 11 is a flow chart illustrating another embodiment of the processof re-transmission of information among RLC layers using the statevariable in accordance with the present invention; and

FIG. 12 is a flow chart illustrating still another embodiment of theprocess of re-transmission of information among RLC layers using thestate variable in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

According to a preferred embodiment of the present invention, the methodfor re-transmitting data or control information of a radio link controllayer in the radio mobile communication system relates to are-transmission process of information by repeating operations oftransmission and checking as predetermined times in case a series ofprocesses of transmitting information, such as data and controlinformation, and receiving checking from the receiver, are failedcontinuously. When the number of transmission is the same as or largerthan a predetermined number as sending of specific information hassuccessively failed, the sender gives up re-transmission and performsthe corresponding error processing process after confirming the lasttransmission of the information has failed.

Particularly, the present invention relates to a re-transmission processby comparing the number of transmission with the critical value (alsoknown as threshold or reference value) when transmission of data orcontrol information has successively failed. When the number oftransmission is the same as or larger than a predetermined number(critical value) as the sending of specific data (RLC PDU) hassuccessively failed, and the transmission of the data transmitted rightbefore has turned out to have failed, the sender sends an MRWinstruction to the receiver.

In addition, when the number of transmission of the MRW instruction isthe same as or larger than MaxMRW, which is the critical or thresholdvalue as sending of the MRW instruction (which is control information)has successively failed, and the MRW instruction which was sent rightbefore has turned out to have failed, the sender sends a resetinstruction for commanding reset of the radio link control layer to thereceiver.

Also, when the number of transmission of the reset instruction is thesame as or larger than the critical value (MaxRST) as sending of thereset instruction (which is control information) has successively failedand transmission of the reset instruction transmitted right before hasturned out to have failed, the sender reports this to the upper layer.

Also, the processes are successively processed and accordingly, when thetransmission of data or control information has successively failed, thenumber of transmission is re-transmitted by comparing it with thecritical value. The method in accordance with the present invention,includes a step in which the sender sends an MRW instruction to thereceiver, when the number of transmission is the same as or larger thana predetermined number as sending of the specific data (RLC PDU) hassuccessively failed, and the transmission of the data transmitted rightbefore has turned out to have failed; a step in which the sender sends areset instruction for instructing reset of the radio link control layerto the receiver, when the number of transmission of the MRW instructionis the same as or larger than MaxMRW which is the critical value assending of the MRW instruction which is control information issuccessively failed, and the MRW instruction which was sent right beforeis turned out to have failed; and a step in which the sender reportsthis to the upper layer, in case the number of transmission of the resetinstruction is same as or larger than the critical value (MaxRST) assending of the reset instruction which is control information issuccessively failed and transmission of the reset instructiontransmitted right before is turned out to have failed.

The process of retransmission of data and control information by thesuggested method is described.

FIG. 7 is a flow chart illustrating the general process forre-transmitting data or information between RLC layers of a sender and areceiver, preferably using the state variable.

In step 71, the state variable is set to 0. The information that needsto be transmitted is transmitted in step 72. In step 73, thetransmission is confirmed by the receiver. If the RLC of the senderreceives the confirmation from the receiver the re-transmission processis terminated. If the RLC of the sender does not receive theconfirmation from the receiver, the state variable is increased by 1, asshown in step 74. In step 75, if the value of the state variable issmaller than the critical or threshold value by comparing the statevariable with the critical value set in advance, the information isre-transmitted, as shown in step 72. Whenever the information istransmitted, the state variable is increased by 1. Finally, when thestate variable becomes same as or larger than the critical value, theretransmission process is terminated, and the sending and receivingsetting is converted to perform a new process.

In FIG. 7, the state variable is increased by 1 if the transmission wasnot successful after checking the transmission status. However, in analternative embodiment, the step of checking of the transmission statusand the step of increasing the state variable may be changed withoutdeviating from the gist of the present invention. The order of the stepsshould be the cycle of transmitting information, checking thetransmission failure with exit, and counting the transmission numberwith exit. If the exemplary embodiment sets the cycle as transmittinginformation, counting the transmission number with exit, and checkingthe transmission failure with exit, the exemplary embodiment could notcheck the failure of the transmission before the escape through the exitof transmission number counting.

FIG. 8 is a flow chart illustrating the process of re-transmission ofRLC PDU using the state variable VT (DAT) using the re-transmissionprocess generally illustrated in FIG. 7.

As shown in the drawing, when the PDU is generated in the RLC layer, thevalue of the state variable VT (DAT) indicating the number oftransmission of the corresponding PDU is set as 0 (step 81).

Then, the corresponding PDU is transmitted and whether the transmittedPDU is successfully received is checked in step 83. If the transmissionis successful, the re-transmission process terminates. If the successfultransmission cannot be verified or checked, the state variable VT (DAT)corresponding to the information is increased by 1 in step 84. The statevariable is then compared with the critical value MaxDAT in step 85.When the value of the VT (DAT) is smaller than the critical value(MaxDAT), the corresponding PDU is re-transmitted, then there-transmission is checked and the value of the VT (DAT) is increased by1, if the successful transmission cannot be verified or checked. (steps82, 83, 84 and 85).

When the value of the VT (DAT) is the same as or larger than thecritical value MaxDAT, the sender stops the retransmission process ofthe corresponding PDU and performs the MRW instruction in step 86.

With the above method, the number of the RLC PDU transmitted until thevalue of the VT (DAT) becomes MaxDAT, is the same as in the conventionalmethod. However, because the successful transmission of the PDU ischecked prior to the checking of the state variable, the last RLC PDUtransmitted is not wasted. In other words, the number of re-transmissionis the same but whether the transmission of the last PDU was successfulis first checked, thus preventing the last PDU from being transmittedunnecessarily. Also, even through the value of the MaxDAT is set to “1”,the problem presented in conventional method no longer occurs.

FIG. 9 is a flow chart illustrating the process of re-transmission ofthe MRW instruction using the state variable VT (MRW) in there-transmission process.

As shown in the drawing, the transmission process is terminated when apositive response about the corresponding MRW instruction until theTimer_MRW is expired after sending the MRW instruction, as successivelyshown in steps 91, 92 and 93. When the positive response about thecorresponding MRW instruction is not received within a predeterminedperiod, the value of the state variable VT (MRW) is increased by 1 instep 94, Then, the value is compared with the critical value MaxMRW instep 95. When the value of the VT (MRW) is smaller than the criticalvalue, the same MRW instruction is re-transmitted to the receiver instep 92. If the value of VT (MRW) becomes the same as or larger than thecritical value, the error processing process, such as reset of the RLClayer, is performed in step 96.

According to the above method, the number of the MRW instructions whichwere transmitted to a receiver until the RESET PDU was transmitted asthe value of the VT (MRW) reaches MaxMRW, is the same as in theconventional method. As a result, the last transmitted MRW instructionis not wasted. Also, even if the value of MaxMRW is set as “1,” theprocessing error associated with conventional method as described abovedoes not occur.

FIG. 10 is a flow chart showing the re-transmission process of the resetinstruction of the RLC layer using the state variable VT (RST).

As shown in the drawing, when a positive response about thecorresponding RESET PDU is received until the Timer_RST is expired aftersending the RESET PDU, the process of re-transmission is terminated(steps 101, 102, 103). When the positive response about thecorresponding RESET PDU is not received, the value of the VT (RST) isincreased by 1 in step 104. The value is then compared with the criticalvalue (MaxRST) in step 105. When the value of the VT (RST) is smallerthan the critical value, the same RESET PDU is re-transmitted to thereceiver in step 102. If the value of VT (RST) becomes the same as orlarger than the critical value, this is reported to the upper layer instep 106.

By the above method, the number of the RESET PDU transmitted until theVT (RST) becomes MaxRST, is the same as in the conventional method.However, the final RESET PDU transmitted to a receiver is not wasted.Also, even if the value of the MaxRST is set as “1”, the errorassociated with the conventional method does not occur.

FIG. 11 is a flow chart illustrating another embodiment of the processof re-transmission of information between RLC layers of a sender and areceiver using the state variables. In this embodiment, the step ofincreasing the state variable precedes the step of checking thetransmission success in comparison with the steps depicted in FIG. 7.Although the state variable is increased before checking thetransmission success, this does not increase the processing burden ofeither the network system or mobile equipment. When the transmission issuccessful and verified, this means that unnecessary calculation isperformed only once more. So, processes of transmitting of informationand changing the state variable may be performed successively orsimultaneously.

FIG. 12 is a flow chart illustrating yet another embodiment of theprocess of re-transmission of information between RLC layers of a senderand a receiver using the state variables.

The cycle of the main steps in FIGS. 7 and 11 is transmittinginformation, checking the transmission failure with exit, and countingthe transmission number with exit. If processing steps are performeddifferently, then the preferred embodiment of the present inventioncannot check the failure of the transmission before the escape throughthe exit of transmission number counting. FIG. 12 shows another flowmaintaining the main cycle of the steps of present invention method.

In the embodiment illustrated in FIG. 12, the comparison between thestate variable and the critical value is performed before the initialtransmission of information. The number of transmission of informationin the above process is the same as in the other embodiments. The methodshown in FIGS. 11 and 12 may be applied in the re-transmission processof the RLC PDU or the MRW instruction, or in the process ofretransmission of the reset instruction of the RLC layer.

Referring to FIG. 12, a state variable is initialized in step 121. Thestate variable is then compared with a critical value in step 122. Ifthe state variable is less than the critical value, then theinformation, such as PDU or MRW or Reset, is transmitted to a receivingdevice in step 123. The state variable is then increased by anincremental value, such as one, in step 124. If the transmission issuccessful then the retransmission is not needed. Otherwise, theretransmission process as described above needs to be repeated. Thedetermination of the successful transmission is determined, for example,by checking whether the successful receipt (or negative acknowledgment)has been acknowledged within a fixed time period using a timer. If thetimer expires before the success acknowledgement is received, then there-transmission process has to be repeated. If the state variable is thesame or larger than the critical value, then the retransmission cycle isended and the sending and receiving setting is converted to perform anew process as shown in step 126.

Using FIG. 12 and using one of state variable, namely, MRW as an example(the variables are used in FIG. 9 to describe one embodiment of thepresent invention), VT(MRW) is initialized in step 121. The VT(MRW) isthen compared with a critical value in step 122. In this case, thecritical value is MaxMRW. However, MaxMRW may be increased or decreasedas system requirement dictates. If VT(MRW) is less than MaxMRW, then theMRW information is transmitted to a receiving device in step 123.VT(MRW) is then increased by an incremental value, such as one, in step124. If the transmission is successful, then the retransmission is notneeded. Otherwise, the retransmission process as described above needsto be repeated. The determination of the successful transmission isdetermined, for example, by checking whether MRW-ACK is received priorto the expiration of Timer_MRW (shown in FIG. 9). If successful, thenthe RLC starts transmission of RLC PDU under a new receiving window.

If VT(MRW) is the same or larger than, for example, MaxMRW, then RLCreset procedure is performed as shown in step 96.

In the above described inventions, the method for re-transmitting dataor control information by the state variable has been described.

As described above, with the method for re-transmitting data or controlinformation using the state variable in accordance with the presentinvention, unnecessary transmission of data or control information canbe reduced and errors are eliminated which can occur in a systemdesigned to transmit the respective information just once. As a result,an efficient and stable system is rendered.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

1. A method for transmitting information of a radio link control (RLC)layer in a radio communication system, the method comprising:transmitting, from a user equipment (UE) to a receiving device, data orcontrol information of the RLC layer; determining, at the UE, whetherthe transmission of the data or control information was unsuccessful;only if the transmission was determined as being unsuccessful, comparinga number of transmissions of the data or control information with avalue associated with a maximum number of transmissions; only if thenumber of transmissions of the data or control information is less thanthe value associated with the maximum number of transmissions, repeatingthe transmitting, the determining, and the comparing operations; and ifthe number of transmissions of the data or control information is equalto the value associated with the maximum number of transmission,providing an indication to an upper layer.
 2. The method of claim 1,wherein the transmission of the data or control information isdetermined as being unsuccessful if a response comprising a negativelyacknowledge (NACK) signal is received at the UE from the receivingdevice.
 3. The method of claim 1, further comprising receiving, at theUE, a response from the receiving device, the response comprising astatus Protocol Data Unit (PDU).
 4. The method of claim 1, wherein thedata or control information relates to an Acknowledged mode data (AMD).5. The method of claim 4, wherein the data or control information of theRLC layer comprises at least one of user data unit, a Move ReceivingWindow (MRW) command or a reset command.
 6. The method of claim 5,wherein the user data unit is an Acknowledged Mode Data (AMD) ProtocolData Unit (PDU).
 7. The method of claim 6, wherein the number oftransmissions of the data or the control information is associated withtransmission of a sequence number of the user data unit.
 8. The methodof claim 1, wherein the data or control information of the RLC layer isretransmitted only once.
 9. The method of claim 1, further comprisingterminating the method if the transmission was determined as beingsuccessful.
 10. The method according to claim 1, wherein the upper layeris a protocol layer that is above the RLC layer.
 11. The methodaccording to claim 1, wherein the indication comprises a report relatingto transmission failure of the data or control information.
 12. A methodfor transmitting information of a radio link control (RLC) layer in aradio communication system, the method comprising: comparing a number oftransmissions of data or control information of the RLC layer with avalue associated with a maximum number of transmissions; only if thenumber of transmissions of the data or control information is less thanthe value associated with the maximum number of transmissions,transmitting, from a user equipment (UE) to a receiving device, the dataor control information of the RLC layer and determining, at the UE,whether the transmission of the data or control information wasunsuccessful; only if the transmission was determined as beingunsuccessful, repeating the comparing, the transmitting, and thedetermining operations; and if the number of transmissions of the dataor control information is equal to the value associated with the maximumnumber of transmission, providing an indication to an upper layer. 13.The method of claim 12, further comprising: initializing the number oftransmissions of data or control information to a value of zero beforecomparing the number of transmissions of data or control information.14. The method of claim 12, further comprising: incrementing the numberof transmissions of data or control information after transmitting thedata or control information and before determining whether thetransmission was unsuccessful.
 15. The method of claim 12, furthercomprising: incrementing the number of transmissions of data or controlinformation after comparing the number of transmissions of data orcontrol information and before transmitting the data or controlinformation.
 16. The method of claim 12, further comprising: only if thenumber of transmissions of the data or control information is equal toor greater than the value associated with the maximum number oftransmissions, changing a setting for sending and receiving the data orcontrol information of the RLC layer.
 17. The method of claim 12,further comprising: terminating the method upon determining that thetransmission was successful or when the number of transmissions of thedata or control information is equal to or greater than the valueassociated with the maximum number of transmissions.
 18. The method ofclaim 12, wherein the data or control information of the RLC layercomprises at least one of a user data unit, a Move Receiving Window(MRW) command or a reset command.
 19. The method of claim 12, whereinthe number of transmissions of the data or control information isassociated with transmission of at least one of a user data unit, a MoveReceiving Window (MRW) command or a reset command.
 20. The method ofclaim 12, wherein the value associated with the maximum number oftransmissions is associated with transmission of at least one of a userdata unit, a Move Receiving Window (MRW) command or a reset command. 21.The method according to claim 12, wherein the upper layer is a protocollayer that is above the RLC layer.
 22. The method according to claim 12,wherein the indication comprises a report relating to transmissionfailure of the data or control information.
 23. A user equipment (UE)for transmitting information in a radio communication system, the UEcomprising: a radio link control (RLC) layer; and a processor configuredto: transmit data or control information of the RLC layer to a receivingdevice; determine whether the transmission of the data or controlinformation was unsuccessful; compare, only if the transmission wasdetermined as being unsuccessful, a number of transmissions of the dataor control information with a value associated with a maximum number oftransmissions; repeat, only if the number of transmissions of the dataor control information is less than the value associated with themaximum number of transmissions, the transmit, the determine, and thecompare operations; and if the number of transmission of the data orcontrol information is equal to the value associated with the maximumnumber of transmission, provide an indication to an upper layer.
 24. TheUE according to claim 23, wherein the upper layer is a protocol layerthat is above the RLC layer.
 25. The UE according to claim 23, whereinthe indication comprises a report relating to transmission failure ofthe data or control information.